Snap-acting switch



Sept' 4, 1934 J. A. SPENCER 1,972,363

SNAP ACTING SWITCH Filed April 4. 1932 Patented Sept;`

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John A.Spencer,` Newtonville, Mass., assignorto General Plate Company,Attleboro, Mass., a cof-'- poration of Massachusetts switch,.whichiseconomical in manufacture and simple and positive in action. Otherobjects will 1`6 be in part obvious and in part pointed out hereinafter.

" v Ihe invention accordingly comprises the 4ele.

'ments and, combinations of elements, features of construction, andarrangements of parts which will be exempliiiedin the structurehereinafterv described, and-the -scope of the application of whichwill'be, indicated inthe following claims.

In the accompanying drawing, in which illustrated several of'variouspossible embodiments of 25.' the invention,

Fig. 1 .is a plan view of a snapacting switch j embodying .theinvention;

Fig. 2 is a cross-section taken substantially on line'2'-2 of Fig;1;and,. Fig-3 is a cross-section taken substanuaiiy on 'line 3 3 of Fig.1.

Similar reference characters indicate -corre spending parts throughoutthe vseveral views of the drawing,

In my Patent No. 1,895,590, dated January 81, .1933, fo'r Snap-actingdevices (application for which was filed July 26, 1930, and which wasthus copending herewith), I have'show-nv an improved form of snap-actingdevicel which includes as a 40 feature, radial .corrugations, whereby anincreased amount of resilient material is present .in theregion wheredisplacements take place .under change' from one to another position.The present .invention -comprises an electric switch including athermostat which is an improvement over the radially corrugated deviceillustrated in said copending application. .The invention will bedescribed principally' by reference to its thermstatic embodiment, thatis,` where it performsink response to temperature changes. However, it

will be understood that, even as a'thermostat,

. the invention is fundamentally a snap-acting device.

Referring now .more particularly to Fig. 1, there is illustrated atnumeral 1, the interior, dished or` cup or concave 'radially corrugatedregion comprising. the operative portion of athermostatic embodiment ofthe present invention. This portion 1 is .preferably formed from aseamless cylinder o'f composite thermostatic metal in 601 the manner.set -forth in said copending applica'- A tion, which comprises, brieily,longitudinally corrugating a cylinder of thermostatic metal andconstricting said corrugated cylinder at one end. as well as compressinglongitudinally until substantially a truncated concor dished disc is-kobtained.

The .term composite thermostatic metal.is used herein.to dei-lneadnaterial composed of materials having relatively differentcoeflicients of. thermal-expansion. type of thermostat is frequentlytermed. bimetallic, The principle' upon which the thermostat operates isthat under varying conditions of'hot andcoldone layer of the compositemetal will exhibit a relatively greater or less tendency to expand thanthe other layer, and thereby build up a stress in the bodywhich the twometals form.'

The-stress'thus set up grows with increased temperature until'strainsare. effected whereby the disc reverses curvature witha snap. That is,if the Ydisc'or dish xor the like was originally con-1 cave, relative toits original conformation it becomes convex, or viceversa. v

' The 'radial 'corrugations in the present thermo- 8.5

stat; as in the thermostat of said copending application, areadvantageous -in that they provide -an increased amount of thermostaticmetal in the central portion. of said disc, and, when the thermostat isbrought to a condition in which it'is aboutto snap, it eiects anincrease in the amount of displaeementthrou'gh which the vcenter of 'thethermostat operates. This increased displace'- ment is highly'advantageous when the thermostat is utilized, forjexample, inelectrical equip- .95. ment, for making and breaking electrical con--`tacts.

- The present invention contemplates the forma-Y tion of a radiallycorrugated disc such vas illustrated in my copending application, andthe 10Q provision thereon -ofA a substantially at, or un-. corrugatedrim or circumferential portion 3.. 'A theremostat produced according tothe present invention has theiollowing advantages: First, the inherenttendency of the thermostat 105 to expand radially, and thereby todecrease its' kinematic eiciency, is limited and controlled'by therelatively non-expansible rim or conning portion 3. That is, withthermostats of the type a shown in said copending. applicatiom'there isa 110.

tendency upon heating for straightening of the sinuous edge, with theresult that the constrictive function of the periphery is reduced a'ssnap action occurs. Hence the thermostat functions more sluggishly thanif the edge were to maintain a more constant restrictive characteristic.The flat rim portion 3 of the present invention, having no corrugationstherein, has substantially no tendency to stretch, and it accordinglybetter serves as a restricting or confining or binding means for theremainderof the thermostat. That is to say, there are no undulations inthe periphery to provide resiliency.

The thermostatic element as thus described is provided with certainadjunctive elements for converting it into an electric switch. As shownin the present drawing, these adjunctive elements are analogous to thoseshown in my Patent No'. 1,718,716, dated June 25, 1929, and comprise abottom supporting plate 12, and a top supporting plate 1 3, each'havinga central aperture there.

through, within which there is located a tubular clamping member 14. Theclamping member 14 is provided with an annular shoulder at the bottomthereof and is made substantially longer than the combined thickness ofthe two plates 12 and 13, to secure the two plates in proper operativeposition in face to face relation. The periphery of the upper end of thetubular member 14 is compressed to provide an annular portion 15 overfhanging the top plate 13.

The plate 12 is provided with a plurality of spaced openings 16, and theplate 13 is provided with a plurality of spaced'openings 17, theopenings 17 being coaxial with lthe openings 16, and of smallerdiameter. (See Fig. 3).

A plurality of contact plates 27, 28, 29 and 31 are operativelysupported by the supporting plate assembly and are located against theouter surrivet members 32 having an enlarged head 33, andl extendingthrough the respective coaxial openings 16 and 17 in the plates 12 and13, adisc 34 of electric insulating material, such as mica, serving toinsulate the head 33 from the plate 13, and serving also to position thebody of the rivet 32 lin the opening 17 and to maintain it coaxialtherewith. This construction is more particularly shown in Fig. 3 in thedrawing.

The cooperating, or circuit completing contacts 4are mounted on thebroad, nat rim portion 3 of the thermostatic disc 1.

The disc 1 is adjustably mounted in substantially parallel-spacedrelation tothe supporting plate assembly. This mounting comprises alshouldered screw-threaded stud 36 that projects through the internallyscrew-threaded tubular clamping membery 14 and that has a flanged member37 located close to one end thereof. A nut 38 is provided adjacent to,A

but spaced from, the ange'37, and the disc 1 is loosely mounted betweenthe nut 38 and flange 37 to permit of a turning movement of the studrela--- vof a stud member 4,3.

order to permit of holding the stud 36 while a lock-nut 41 istightenedto prevent any further turning movement of the stud 36 -afterproper adjustment has once been. made.

A plurality of contact bridging members 42 are supported by thethermostatic disc 1, by means members 42 is adequately described in saidPatent 1,718,716, and requires no particularization herein.

To align the disc and base members, a stud 53 is mounted in said basemembers and projects through an opening 55 in the rim 3 of the disc 1.The contacting members 42 are thus maintained in proper relationship tobridge the members 27,

The construction of the 28, 29, and 31 when the disc 1 snaps tocontactclosing position. l

It is to be understood that I am aware that a substantially at rim has aslight capacity to stretch but it is to be noted that such capacity ismuch less than the corresponding capacity in an undulatory or sinuousrim. In thecase of the flat rim the stretch eiects only a tensilestress,

i whereas in the undulatory'rim a bending moment as for instanceindependent bindingrims, wires andthe like. It also includes integraland other rims wherein the material is disposed notquite atly but insuch a manner that peripheral or lateral stretching at the outer ends ofthe radial or other corrugations is substantially reduced. For instance,the peripheral band 3 may have stiffening bulges or indentations or thelikel which are independent of the radial corrugations. However, theform disclosed is preferable in the present embodiment.

If the invention is to be employed as a simple mechanical snap-acting orovercentering switch, or spring-type switch, it will readily be seenthat the use of composite metal is unnecessary, although possible. Insuch instances, sheet of single resilient metal may be used withsuccess. The action of the device as an overcentering switch needs nofurther description, as it varies from the thermostatic switch only inthat applied external forces replace the self-engendered thermostaticforces in effecting the change of shape desired.

In` view of the above, it will be vseen that the several objects oftheinvention are achieved and other advantageous results attained.

As many changes could be made in carrying outthe above constructionswithout departing" from the scope of the invention, it -is intended thatall matter contained in-the above description or shown in theaccompanying drawing shall be interpreted as illustrative and not inahunting sense.

I- claim:

1. A switch including a radially corrugated,

snap-acting thermostat having a relatively nat' peripheral region andvcontacting buttons carried on said relatively at portion.

2. -A thermostatic switch unit comprising a radially corrugated sheet ofcomposite thermostatic material, said sheet being provided with anintegral confining rimof substantially flat material and contactingbuttons carriedon said rim,

3. In an electric switeh, a thermostatic actuator comprising a sheetofcomposite thermostatic metal having corrugations therein', and meansconiining expansion along said corrugations, said means carryingcontacting buttons adapted to make and breakelectrical connectionsaccording to the relative position of said -actuator.

4. In an electric switch, a thermostatic actu-` ator comprising a discof composite thermostatic metal, said disc having radial corrugat'ionstherein, and an uncorrugated rim portion on said disc, said rim portioncarrying contacting buttons adapted to make and break electricalconnections according to the relative position of said actuator.

5. An electric switch comprising a base mem ber, terminal piecesarranged on said base member, a thermostatic actuator comprising a sheetof composite thermostatic metal having corrugations therein and formedto have two positionsof stable equilibrium, and having an uncorrugatedconning rim portion, means mounting said actueral, uncorrugated rirnportion, means mounting said actuator in spacedrelationship to said basemember, and one or more contacting buttons carried on said rim portionand positioned to 1 complete an electric circuit between said terminalson said base portion.

7. An electric switch comprising a base member, terminal pieces arrangedon said base member, a thermostatic actuator comprising a sheet ofcomposite thermostatic metal having corrugations therein and formed tohave two positions of stable equilibrium, means mounting said actuatorin spaced relationship to said base member, and one or more contactingbuttons carried on said actuator and positioned to complete anelectrical circuit between said terminals on said base portion.

8. An electric switch comprising a base member, terminal pieces arrangedon said base meinber, a thermostatic actuator comprising a disc orcomposite thermostatic metal having radial corrugations therein andformed to have two positions of stable equilibrium, means' mounting said80 actuator in spaced relationship to said base member, and one or morevcontacting buttons carried on said actuator and positioned to completean electrical circuit between said terminals on said base portion.

9. In a snap-acting electric switch, a snap-aoting actuator comprising adisc of resilient material having radial corrugations therein, the planeof the central portion .of said disc being displacedy from the plane ofthe peripheral -portion thereof, the said disc being suitably resilient,whereby upon suitable actuation thereof, it overcenters to assume aposition of opposite configuration, and electrical contacting meanscarried by said disc.

l0. In a snap-acting electric switch, a snap- '95 acting actuatorcomprising a disc of resilient material1 having radial ,corrugationstherein, lthe plane of the central portion of said disc being d isplacedfrom the plane of the peripheral portion thereof, the said disc beingsuitably resilient, whereby upon suitable actuation thereof, itovercenters to assume-a position of opposite configuration, and meansconning expansion along said corrugations, said means carryingelectrical contacting means adapted to make and break electricalconnections .according to the relative position of said actuator.

ll. An electric switch comprising a base member, at least one terminalpiece arranged on said base member, a snap-acting actuator comprising adisc of resilient materialhaving radial corruga- -tions therein, theplane of the central portion of said disc being displaced from the planeof the peripheral portion thereof, said disc being suitably resilient,whereby upon suitable actuation thereof, it overcenters to assume aposition of opposite configuration, means mounting said actuator inspaced relationship to said base member, and at least one electricalcontacting means carried on said actuator and positioned to cooperatewith f the terminal piece on said base member to control an electricalcircuit.

JOHN a. SPENCER.

